Congestive heart failure (CHF) can be characterized as an inability for the heart to provide sufficient oxygenated blood to meet metabolic demand. For example, weak myocardial tissue can impair heart function, such as resulting in a diminished capacity to pump and circulate blood into pulmonary or systemic circulation. CHF can be accompanied by circulatory impairment resulting in a failure to deliver adequate blood and oxygen supply to peripheral tissues, including vital organs. CHF can become progressively more severe and, if left untreated, can be fatal.
Beck et al., U.S. Patent Application No. 2011/0201943, titled “KINETICS OF PHYSIOLOGIC RESPONSE TO ACTIVITY DURING ACTIVITIES OF DAILY LIVING,” refers to using a physiologic response to activity during activity to generate useful diagnostic information about a subject. Beck et al., U.S. Patent Application No. WO/2007/011565, titled “MONITORING PHYSIOLOGIC RESPONSES TO STEADY STATE ACTIVITY,” refers to systems and methods for monitoring physiologic responses to a steady state activity.